What are the intracellular locations and movements of Vitamin A compounds during the visual cycle and rod renewal cycle, and what are their functions? By injecting radioactive Vitamin A compounds into rats and co- chromatographing extracts of ocular tissues with marker compounds on thin layer plates we can determine the location of Vitamin A compounds during the visual cycle (bleaching and regeneration of rhodopsin) and rod renewal cycle (synthesis and degradation of rod outer segment discs). Using techniques of subcellular fractionation by sucrose density gradient centrifugation, we can simultaneously characterize subcellular particles enzymatically and assay their content of Vitamin A compounds. By exposing one eye of an injected rat to controlled light signals and not the other, we can use the subsequent difference between the two eyes in the distribution of radioactivity in Vitamin A compounds as a measure of the relationship between the turnover Vitamin A compounds and the rod renewal and visual cycles. How and where is rhodopsin synthesized and localized during renewal of the rod outer segment discs? Specifically, we want to known what kind of ribosomes are involved (free or membrane bound), where the phospholipid carbohydrate and chromophore (11-cis retinal) components are added, and how the highly insoluble pigment is transported to the site of its incorporation into the disc membranes (or is it made right there). We want to approach these questions first by a thorough subcellular fractionation by sucrose-Ficoll continuous density gradient centrifugation and enzymatic characterization of subcellular particles (microsomes, mitochondria, rod outer segments, plasma membrane, lysomes, Golgi-body). Then we will pulse label retinas in vitro with radioactive precursors of rhodopsin components, and characterize the synthesized products as they move through the cellular particulates by methods of SDS gel electrophoresis and column and thin-layer chromatography.